JPH10104819A - Phase shift mask and method for forming the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of phase conflict and the bridging at line ends by providing the ends of the opaque lines of a phase shift mask with opaque fine chips or triangular segments. SOLUTION: The parallel opaque lines 22 are formed on a transparent mask substrate consisting of quartz, etc. The triangular segments 40 are formed at the respective ends of the opaque lines 22 and have the base width equal to the width 34 and height 36 of the opaque lines 22. A phase shift material 24 has a phase shift of about 180 deg. for the purpose of light to illuminate the mask. The respective opaque lines 22 are formed between the paired parallel opaque lines 22 in such a manner as to be adjacent to only one region of the phase shift material 24 and the one region of the transparent material 20. If the ratio of the height 36 to the base width 34 of the opaque fine chips 40 is about 2 to 5, the abrupt phase shift between the respective phase sift regions of 0 deg. and 180 deg. where the bridging is induced between the ends of the adjacent lines is prevented by the opaque fine chips 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask which does not cause a phase conflict problem and a method of forming the same, and more particularly, to a space exposed on a wafer using a bright field line and a positive photoresist. The present invention relates to a phase shift mask and a method of forming the phase shift mask in which a bridge problem does not occur due to a phase conflict in a Levenson phase shift mask between the pattern and the pattern.

[0002]

2. Description of the Related Art When forming a large number of small parallel and parallel lines and spaces bright field pattern on a semiconductor integrated circuit wafer, if the pattern size exceeds the limit of the resolution of the irradiation (exposure) wavelength, In particular, a phase shift mask is often used. 0 ° phase shift region and 180
The phase conflict problem between the regions of phase shift creates a bridging problem at the edges of these patterns.
U.S. Patent No. 5,468,5 to Rolfson
No. 78 describes a method in which a plurality of mask patterns are formed using a mask pattern having an opaque region and a transparent region, and adjacent transparent regions of the mask pattern are combined, thereby preventing a phase conflict. Is disclosed.

US Pat. No. 5,318,868 to Hasegawa et al. Discloses the use of phase shifting materials with different transmittances in different areas of the mask. Marc D. Levenson
Levenson), "Phase Shift Mask Strategy: Separated Dark Lines" (Microlithography World
ographyWorld), March / April, 1992, 6-12
P.) Discloses a method for patterning isolated dark lines. Bridges at the phase transition are discussed as using a fine point at the end of the phase shift region to control the bridge. Mark Dee
Marc D. Levenson's paper "Strategy for Phase Shift Masks: Line Space Patterns" (Microlithography World, 9
Mon / October, 1992, pp. 6-12)
A method for patterning a space pattern is disclosed. Bridges at the phase transition are discussed as using additional 60 ° and 120 ° phase shift layers to control the bridge.

The present invention relates to a phase shift mask that prevents the occurrence of phase conflict problems by forming opaque fine points at the ends of finely spaced parallel opaque lines. Fine points at the edges of the phase shift region have the problem of residual resist left on the semiconductor wafer when the mask is used to form an equi-line space bright-field pattern. This problem is prevented by using opaque fine points at the ends of the finally spaced parallel opaque lines. The invention also relates to a method for forming a phase shift mask.

[0005]

Since the minimum feature length for manufacturing a semiconductor integrated circuit wafer has been reduced to the submicron range, a large resolution is required for a mask used for photolithographic processing. . Phase shift masks are often used to increase the resolution limits of these masks. If the pattern transferred from the mask to the wafer has a series of parallel lines,
Grating patterns with a series of parallel lines can be used. In these cases, the mask has a series of parallel opaque lines with spaces between them. A conventional mask of this kind is shown in FIG. That is, FIG. 1 shows a conventional mask in which parallel opaque lines 12 having spaces 14 therebetween are formed on a transparent mask substrate 10. The opaque line 12 is shown by an oblique shadow line.

[0006] Phase-shifting materials are often used to improve the resolution of masks of the type shown in FIG.
As shown in FIG. 2, the parallel opaque lines 22 are
0. Phase shifting material 24 is formed in the spaces between the alternating pairs of lines. In FIG. 2, as in all other plan views herein, opaque areas are shown with oblique shadows, phase shift areas are shown with horizontal shadows, and 0 ° phase shift transparent areas are shown with shadows. Not indicated by line. As shown in FIG. 2, the remaining space 21 between the opaque lines 22 or adjacent to the outermost opaque line is
It has only a transparent material. This type of mask is often referred to as a Levenson or alternating aperture phase shift mask. The use of the alternating aperture phase shift mask shown in FIG. 2 with a positive resist on a semiconductor wafer causes problems due to phase conflicts at the line ends. This phase conflict results from an abrupt change from phase shift material to transparent material at the end of a line pair with the phase shift material between them. As shown in FIG. 3, this phase conflict results in a bridge pattern 74 at the end of the line 72 formed on the semiconductor wafer 70.

[0007] Other methods have been used to prevent the problem of phase conflicts occurring at the ends of opaque lines. FIG. 4 shows that 3 is located at the end of the phase shift region of the mask.
FIG. 1 shows a plan view of a conventional mask using a phase fine chip having angular sections. FIG. 5 shows a plan view of a conventional mask using 60 ° and 120 ° phase shift steps at the edges of the phase shift region of the mask. FIG. 4 shows a mask that uses a fine phase chip to prevent the occurrence of a phase conflict problem. The phase shift material 24 that provides a 180 ° phase shift is indicated by a horizontal shaded line. The opaque material 22 is shown with diagonal shadow lines. Opaque line 22 and phase shift line 24
Are formed on a transparent mask substrate 20. Bottom 2
A triangular section 25 having a height of 7 and a height 28 is formed at the end of the phase shift line. When the ratio of the height 28 to the base width 27 becomes equal to about 3, the bridging problem occurring at the end of the line is prevented. However, this method has a problem that when an equiline and space bright field pattern is formed using a mask, a residual resist is generated on a semiconductor wafer.

FIG. 5 is a plan view of a mask using a 60 ° phase shift region 32 and a 120 ° phase shift region 30 at the end of a 180 ° phase shift line 24 formed on a transparent mask substrate 20. is there. In FIG. 5, the opaque regions 22 are shown by oblique shadow lines, the 180 ° phase shift regions 24 are shown by horizontal shadow lines, the 120 ° phase shift regions 30 are shown by vertical shadow lines, and 60 ° The phase shift region 32 is indicated by a horizontal dashed shadow line. In this mask, since there is a gradual transition from a phase shift of 180 ° to a phase shift of 0 °, the occurrence of a phase conflict problem is prevented. However, this method has the problem that the cost and complexity are increased because extra levels of 60 ° and 120 ° phase shift must be formed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a phase shift mask for forming a parallel line which prevents a phase conflict and a bridge at a line end. Another object of the present invention is to provide a method of forming a phase shift mask for forming parallel lines for preventing the occurrence of phase conflicts and bridges at line ends.

[0010]

In order to achieve the above object, a phase shift mask according to the present invention has an opaque fine chip or triangular segment at an end of an opaque line of the phase shift mask. It is characterized by. In the present invention configured as described above, the opaque fine chip prevents the occurrence of the phase conflict problem, and further prevents the occurrence of the residual photoresist and the extra phase shift levels of 60 ° and 120 °. .

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a phase shift mask of the present invention using a fine opaque chip will be described with reference to FIGS. FIG. 6 shows parallel opaque lines 22 made of a material such as chrome, which parallel opaque lines 22 are transparent, such as quartz.
It is formed on a mask substrate. In FIG. 6, opaque areas are indicated by oblique shadow lines, and 180 ° phase shift areas are indicated by horizontal shadow lines. A triangular segment 40 is formed at each end of the parallel opaque line 22, and each triangular segment 40 has a width 34 of the parallel opaque line 22.
And a base width equal to the height 36. The phase shift material 24 has a phase shift of about 180 ° for the light used to illuminate the mask,
4 is formed between a pair of parallel opaque lines 22 such that each opaque line 22 is adjacent to only one region of phase shift material 24 and one region of transparent material 20. The edge of each region of phase shift material 24 expands to fill the region between corresponding opaque microtips 40.

The mask of FIG. 6 is used to form parallel lines and spaces on a semiconductor wafer using a positive photoresist that forms a line and space pattern. When the ratio of the height 36 to the base width 34 of the opaque microtip is about 2 to 5, the opaque microtip provides a 0 ° phase shift region that creates a bridge between the ends of adjacent lines. A sharp phase shift during the 180 ° phase shift region is prevented. FIG. 7 is a cross-sectional view of the phase shift mask taken along line 7-7 ′ of FIG. This phase shift mask uses an opaque fine chip. In this phase shift mask, the phase shift pattern is etched in the transparent mask substrate, and the thickness of the transparent mask substrate is different, so that the phase shift is different by 180 °. At the mask portion of the transparent mask substrate, a material such as quartz is removed by etching, and the transparent substrate material 24 is used to form a phase shift region. The opaque region 22 is formed of a material such as chrome.

FIG. 8 is a sectional view of the phase shift mask taken along line 8-8 'of FIG. This phase shift mask uses an opaque fine chip. In this phase shift mask, a phase shift material is formed on a transparent mask substrate to give a phase shift different by 180 °. In this mask, silicon oxide or spin-on-glass
Are formed on the transparent mask substrate 20 and between the pair of opaque lines 22. The thickness of the phase shift material 24 is adjusted and the wavelength of light used to illuminate the mask, for example, an i-line of 365 nanometers,
248 nanometer krypton fluoride or 193 nanometer argon fluoride gives a phase shift of about 180 °. Next, an embodiment of a method for forming a phase shift mask having an opaque fine chip according to the present invention will be described with reference to FIGS. In this phase shift mask, a phase shift pattern is etched in a transparent mask substrate, and the thickness of the transparent mask substrate is different, thereby giving a phase shift different by 180 °.

As shown in FIG. 9, about 800 to 1400
An opaque layer 21 of a material such as chromium having a thickness of Å is formed on the transparent mask substrate 20. The transparent mask substrate 20 is a material such as quartz having a thickness of about 0.090 inches for a 5 inch reticle (mask pattern in a net) or about 0.25 inches for a 6 inch reticle. Photoresist 50
Is formed on the opaque material 21. Thereafter, a pattern of parallel opaque lines and opaque fine chips is formed on the layer of photoresist 50 by electron beam exposure. Using the photoresist pattern as a mask, the pattern is formed on the opaque chrome layer by wet etching. FIG. 10 shows an opaque mask substrate 2
Opaque parallel lines 20 formed in opaque material on
And the opaque fine chip 40 are shown. FIG. 11 is a cross-sectional view taken along line 11-11 ′ of FIG. 10 and shows a cross-section of an opaque line 22 formed on a transparent mask substrate 20.

Next, as shown in FIGS. 12 and 13, a photoresist pattern 52 is formed over these areas of the transparent mask substrate, and the extra thickness of the transparent mask substrate causes a 180 ° phase shift. Will be given. This photoresist pattern 52 is formed by electron beam exposure of the photoresist layer. FIG. 13 is a sectional view of FIG.
FIG. 13 is a cross-sectional view taken along line -13 ′, showing a transparent mask substrate 20;
3 shows a cross section of a photoresist pattern 52 formed on the upper opaque parallel line 22. Next, as shown in FIG. 14, a portion of the transparent mask substrate 20 which is not covered with the photoresist pattern is partially removed by anisotropic dry etching, and the photoresist is further removed. A portion of the parallel, opaque line pattern 22 becomes part of the etch mask, which automatically matches the etch to the pattern formed in the opaque material. The anisotropic dry etching of the transparent mask substrate is controlled to provide an amount of material that provides a 180 ° phase shift for the wavelength of light used to illuminate the finished mask. The unetched portions of the transparent mask substrate 24 provide a 180 ° phase shift in the completed mask.

Next, FIGS. 9 to 11 and FIGS. 15 to 1
8, another embodiment of the method for forming a phase shift mask having an opaque fine chip according to the present invention will be described.
In this phase shift mask, a phase shift is formed on a transparent mask substrate, thereby giving a phase shift different by 180 °. An opaque parallel line pattern having opaque fine chips is formed in the same manner as in the above-described embodiment (see FIGS. 9 to 11). Next, as shown in FIG. 15, the layer of the phase shift material 60 is
0 is formed so as to cover the opaque line 22. The phase shift material is a material such as silicon oxide or spin-on-glass, and has a thickness that provides a 180 ° phase shift for the wavelength of light used to illuminate the completed mask. Next, the photoresist pattern 5
5 is formed over the layer of phase shift material so as to cover the area of the phase shift material that is left behind to provide a 180 ° phase shift (see FIGS. 16 and 17). A photoresist pattern is formed using the e-beam exposed and grown photoresist layer.

Next, as shown in FIG. 18, the portion of the layer of the phase shift material 62 that is not covered with the photoresist is removed by anisotropic dry etching, and the photoresist is removed. The phase shift material
It remains over the area of the transparent substrate 20 between the alternating pairs of adjacent parallel opaque lines 22 and the opaque microtips. The phase shift material 62 covers a portion of the opaque parallel line 22 so that the end position of the phase shift material is not critical. Phase shifting material 62 provides a 180 ° phase shift. Although the present invention has been described with reference to the preferred embodiments, those skilled in the art can make various changes and modifications within the scope described in the claims.

[Brief description of the drawings]

FIG. 1 is a plan view showing a conventional mask, usually referred to as a binary or chrome mask, having parallel opaque lines forming parallel lines and spaces on a semiconductor wafer.

FIG. 2 is a plan view showing a conventional mask with parallel opaque lines having phase shifting material between pairs of opaque lines and commonly referred to as a Reverson phase shift mask or an alternating phase shift mask.

FIG. 3 is a plan view showing a bridge between adjacent parallel lines on a semiconductor wafer formed using the conventional mask of FIG. 2;

FIG. 4 is a plan view showing a conventional mask using a fine phase chip to prevent the occurrence of a phase conflict problem.

FIG. 5 is a plan view showing a conventional mask in which a phase conflict problem is prevented by using a phase region of 60 ° and 120 °.

FIG. 6 is a plan view showing a phase shift mask using an opaque fine chip according to the present invention.

FIG. 7: 180 different thicknesses of the transparent mask substrate
° Cross-sectional view of the phase shift mask of the present invention using the opaque fine chip on which the phase shift pattern is formed, taken along line 7-7 'in FIG.

FIG. 8-8-8 of FIG. 6 of the phase shift mask of the present invention using an opaque microtip, wherein the patterned layer of phase shift material on a transparent mask substrate forms a 180 ° phase shift pattern; 'Cross section along the line

FIG. 9 is a cross-sectional view showing an opaque material layer and a photoresist layer formed on a transparent mask substrate.

FIG. 10 is a plan view showing an opaque fine chip formed at an end of an opaque line for the mask of the present invention.

11 is a sectional view taken along the line 11-11 'in FIG.

FIG. 12: 180 ° etching of the transparent mask substrate
Plan view showing a photoresist pattern formed over opaque lines on a transparent mask substrate to form a phase shift pattern of

13 is a sectional view taken along the line 13-13 'in FIG.

FIG. 14: Etching a transparent mask substrate to 180
FIG. 2 is a cross-sectional view showing a completed phase shift mask of the present invention for forming a phase shift pattern of °.

FIG. 15 is a cross-sectional view showing a layer of a phase shift material formed on a transparent mask substrate and an opaque line, and showing the opaque line formed on the transparent mask substrate;

FIG. 16 is a plan view showing the opaque lines shown in FIG. 15 and the pattern of photoresist formed over the layer of phase shift material to etch a 180 ° phase shift pattern in the layer of phase shift material.

17 is a sectional view taken along the line 17-17 'in FIG.

FIG. 18 shows 18 etched in the phase shift material
Sectional view showing a completed phase shift mask of the present invention using a 0 ° phase shift pattern.

[Explanation of symbols]

 REFERENCE SIGNS LIST 20 transparent mask substrate 21 opaque layer (opaque material) 22 opaque line (opaque region) 24 phase shift material 34 width 36 height 40 opaque fine chip (triangular segment) 50 photoresist 52 photoresist pattern 55 photoresist pattern 60 phase shift material 62 phase shift material

Claims (25)

[Claims] 1. A transparent substrate; and a plurality of parallel opaque patterns formed on the transparent substrate, each of the opaque patterns comprising two parallel sides and two of these parallel opaque patterns. A width equal to the distance between the parallel sides, an end perpendicular to the two parallel sides, and a triangular area extending from the end, the triangular area being the base and height And a plurality of phase shift patterns formed on the transparent substrate, the plurality of phase shift patterns being formed on the transparent substrate. And a plurality of transparent patterns formed on the transparent substrate, each of the transparent patterns being adjacent to one of the opaque patterns, wherein each of the transparent patterns is the opaque pattern. Adjacent to one of And a transparent pattern as described above. 2. The phase shift mask according to claim 1, wherein said transparent substrate is quartz. 3. The phase shift mask according to claim 1, wherein said opaque pattern is formed of chrome. 4. The phase shift mask according to claim 1, wherein said width is about 0.5 to 2.5 microns. 5. The phase shift mask according to claim 1, wherein said height / width is about 2 to 5. 6. The method of claim 1, wherein said phase shift pattern is formed from spin-on-glass.
The phase shift mask as described. 7. The phase shift mask according to claim 1, wherein said phase shift pattern provides a phase shift of about 180 ° for light having a wavelength of about 365 nanometers. 8. The phase shift mask according to claim 1, wherein said phase shift pattern provides a phase shift of about 180 ° for light having a wavelength of about 248 nanometers. 9. The phase shift mask according to claim 1, wherein said phase shift pattern provides a phase shift of about 180 ° for light having a wavelength of about 193 nanometers. 10. A method of forming a phase shift mask, the method comprising: providing a transparent substrate; forming a layer of an opaque material on the transparent substrate; Forming a first layer of photoresist on the layer; forming a first pattern on the first layer of photoresist; and etching the opaque layer by etching using the first pattern of the first layer of photoresist as a mask. A first pattern is formed in the layer of material, thereby forming a plurality of first pattern elements of opaque material, each of the first pattern elements of opaque material having two parallel sides and A width equal to the distance between the two parallel sides, an end perpendicular to the two parallel sides, and a triangular region extending from the end, the triangular region being the base Have a height A step of removing the first pattern formed in the first photoresist layer; and a step of removing the first pattern formed in the first layer of the photoresist. Forming a second layer of photoresist over the first pattern formed on the layer of material; and forming a second pattern on the second layer of photoresist, wherein the second pattern of the second layer of photoresist is A plurality of second pattern elements, each of the second pattern elements of the photoresist second layer covering a portion of the transparent substrate between two adjacent first pattern elements of the opaque material and Contacting two adjacent opaque first pattern elements so that each of the first pattern elements of the opaque material has only one second pattern element of the photoresist second layer Contacting; etching a portion of the transparent substrate that is not covered by the first pattern formed on the opaque material layer or the second pattern formed on the photoresist second layer by a first depth; And removing the second pattern formed on the photoresist second layer. 2. A method for forming a phase shift mask, comprising: 11. The method according to claim 10, wherein the transparent substrate is quartz. 12. The method according to claim 10, wherein the opaque material is chromium. 13. The method of claim 10, wherein said width is about 0.5 to 2.5 microns. 14. The method of claim 10, wherein the height / width is about 2 to 5. 15. The method of claim 15, wherein the first depth of the transparent substrate is about 180 ° for light having a wavelength of about 365 nanometers.
The method for forming a phase shift mask according to claim 10, wherein the phase shift is given. 16. The method of claim 1, wherein the first depth of the transparent substrate is about 180 ° for light having a wavelength of about 248 nanometers.
The method for forming a phase shift mask according to claim 10, wherein the phase shift is given. 17. The method of claim 17, wherein the first depth of the transparent substrate is about 180 ° for light having a wavelength of about 193 nanometers.
The method for forming a phase shift mask according to claim 10, wherein the phase shift is given. 18. A method of forming a phase shift mask, the method comprising: providing a transparent substrate; forming a layer of an opaque material on the transparent substrate; Forming a first layer of photoresist on the layer; forming a first pattern on the first layer of photoresist; and etching the opaque layer by etching using the first pattern of the first layer of photoresist as a mask. A first pattern is formed in the layer of material, thereby forming a plurality of first pattern elements of opaque material, each of the first pattern elements of opaque material having two parallel sides and A width equal to the distance between the two parallel sides, an end perpendicular to the two parallel sides, and a triangular region extending from the end, the triangular region being the base Have a height A step of removing the first pattern formed in the first photoresist layer; and a step of removing the first pattern formed in the first layer of the photoresist. Forming a phase shift material layer covering the first pattern formed on the material layer; forming a photoresist second layer on the phase shift material layer; and forming a second pattern on the photoresist second layer. Wherein the second pattern of the second photoresist layer has a plurality of second pattern elements, each of the second pattern elements of the second photoresist layer being formed of two adjacent opaque materials. Covering a portion of the transparent substrate between first pattern elements and covering a portion of the first pattern element of two adjacent opaque materials;
A step of covering each said portion of the first pattern element of the opaque material with only one second pattern element of the second photoresist layer; and a step of forming the second pattern element on the second photoresist layer. Etching the portion of the phase shift material not covered by a pattern by etching; and removing the second pattern formed on the photoresist second layer. Forming method. 19. The method according to claim 18, wherein the transparent substrate is quartz. 20. The method according to claim 18, wherein the opaque material is chromium. 21. The method of claim 18, wherein said width is about 0.5 to 2.5 microns. 22. The method of claim 18, wherein the height / width is about 2 to 5. 23. The method according to claim 23, wherein the phase shift material is spin-on.
19. The method according to claim 18, wherein the mask is glass. 24. The method according to claim 18, wherein the phase shift material is silicon oxide. 25. The method of claim 18, wherein the phase shift material has a thickness that provides a phase shift of about 180 ° for light having a wavelength of about 365 nanometers.